Sequel to The Arithmancer. Years 5-7. Armed with a N.E.W.T. in Arithmancy after Voldemort's return, Hermione takes spellcrafting to new heights and must push the bounds of magic itself to help Harry defeat his enemy once and for all.

It was the same reasoning as Dumbledore had had with the shack: avoiding attracting attention. It was also only Bill, Hermione, and Harry—the most essential people for the task. They quickly decided not to bring in anyone else (Bill once again vetoed his siblings). The one person they considered was Sirius. He would have been an asset against aggressive defences, but Bill insisted that anyone who wasn't a cursebreaker themselves on a mission like this was dead weight, and he had two he couldn't leave behind already, so Sirius very anxiously agreed to wait for them with George and Fred and a very cross (and mostly uninformed) Fleur to provide assistance when they returned.

Bill Side-Alonged Harry and led Hermione via Apparition to the site. They arrived to find themselves standing on an outcropping of rocks on the windy shore of the North Sea, at the bottom of a cliff face that loomed ominously above them, black and foreboding, while waves crashed against the rocks mere feet from where they stood.

"You're sure this is the right place?" Hermione said. "Dumbledore said Tom Riddle came here on holiday as a boy."

"Positive," Bill said. "Probably on top of the cliff, but still. I could detect the wards. The cave entrance is just about under us." He pointed with his wand down at something Harry and Hermione couldn't see over the lip of the rock outcropping. "We'll have to swim to it, but it's not far. Just be careful not to hit your head on a rock. Come on. We'll need to hurry and make sure we get through it in plenty of time before the tide comes in."

If it took that long, Hermione thought they would be having more serious problems. Even though she knew that cursebreakers sometimes needed weeks to crack open a tomb, that was more down to forensics and translation. If it took more than a few hours here, it could raise suspicions with You-Know-Who that would make their task much harder.

"How do we get down there?" Hermione asked, eyeing the jagged rocks below sceptically.

Bill produced a coil of rope and tied it to an outcropping. "There's a path around that way," he said, gesturing to the side. "I scouted as far as the entryway of the cave. We could pick out way down without it, but this is easier."

With the skill of a professional, Bill scrambled down the rocks with the aid of the rope to the water level, leaving Harry and Hermione to follow at their own pace. It wasn't that hard with the rope, but when they hit the water, the cold hit Hermione like a lorry. She'd never been swimming in water this cold before, though Harry had much worse off in the Triwizard Tournament. Harry kicked his way over to her and held her head above water long enough to get a Warming Charm off before the shock made her sink.

"Thanks, Harry," she said breathlessly.

"You-Know-Who just couldn't pick a tropical island, yeah?" he said with a grin.

"Would've been smarter—putting it farther away from Britain," she said. "Of course, even smarter would be an underwater vault off the coast of Marie Byrd Land or something, so we should count ourselves lucky."

"Marie who?"

"Marie Byrd Land. It's the Pacific-facing coast of Antarctica—the last major unclaimed territory on Earth. I…may have fantasised about claiming it for a muggle-born-ruled, magitech-powered utopia on occasion."

Harry laughed: "Only you, Hermione."

"Yeah. The scary part is I could see you doing it," Bill agreed. "Anyway, we'd better move." He gave the rope three sharp tugs, and the knot untied itself, and it coiled itself back around his arm. "Don't want to leave a trace," he said.

"Huh. Elvish rope," Hermione observed.

"Huh?" Bill and Harry said.

"Muggle reference. Never mind. Where's the cave?"

"This way," Bill said.

It was a short swim to the mouth of the cave, which was good, as they were still wearing street clothes. Hermione could see what he meant about time. The entrance would be completely submerged at high tide. The tunnel was narrow, and they pushed themselves along the rock walls as much as swam it. It was surprisingly long, too, and would have been pitch black were it not for their wandlight, but Bill didn't lead them astray, and they came to a staircase carved into the rock, leading up into a part of the cave that looked to be permanently dry. It didn't look like much—a bare, rough chamber, eroded naturally out of the rock. Hermione quickly used a Hot Air Charm to dry out her clothes before she got hypothermia, and Harry and Bill followed suit.

"This is as far as I came before," Bill said. "Just far enough to tell there was something behind here. Now, we need to find the entrance." He began waving his wand over the rock face and murmuring softly in various languages. "Dumbledore probably could've done this by touch alone," he muttered. "Anyway. You said there was a blood sacrifice to get into the shack. I'm hoping…aha. Same trick here." He pointed to a nondescript section of rock.

"I've got—" Hermione started to say.

"No," Bill cut her off. "If we're going to save Harry in the end, you're both worth more than I am. Besides, I'm the Cursebreaker here."

Hermione sighed, but he was right. "At least use my stiletto," she said, pulling her black dagger from her boot.

Bill examined the blade and nodded, pronouncing it satisfactory, and pricked his finger, dripping blood on the rock. A few drops later, and an entrance appeared. There was no ominous grinding of rock, as Hermione expected. Instead, a whole arch-shaped section of the wall simply vanished, leaving a black entrance to the chamber within. That…that was high magic, she thought—the thing simply done—a different kind of intimidating from her flashy special effects. She'd have to think on that when she got the chance.

"C'mon. Slowly," Bill said. He stepped into the archway, waving his wand to check for curses all the while.

The inner chamber of the cave was huge—so huge Hermione was certain it must have been magically expanded. Most of the space was taken up by a small lake—black as the Outer Darkness in that underground cavern—with only a narrow path of rock, little more than a catwalk, surrounding it. The only light besides their wands was a sickly greenish glow from some kind of beacon in the middle of the lake. The light wasn't bright enough to see the far side, nor the ceiling, and it was Killing Curse green—the colour of Death.

"Oh, this is pleasant," Hermione muttered.

"Par for the course for You-Know-Who," Bill agreed.

"Do we swim?" Harry asked.

"No. I don't think so. In fact, don't touch the water. I have a bad feeling about it."

"Summoning?" he suggested.

Bill paused and cast a few spells. Suddenly, a pale form leapt out of the water not twenty feet away from them and fell back down with a splash that sounded like a gunshot in the silence. Harry and Hermione both screamed.

"No, no, definitely not," Bill said with a pained sound.

"What—what the hell was that?" Hermione whimpered. She knew what she thought she saw, but it was too horrible for her mind to accept.

"Inferius," he said, grim-faced. "And I'll bet a lot of gold there are a lot more. No magic. Or at least very limited. Nothing that will help us get to the horcrux."

Inferi. Human corpses enchanted to move like a puppet and act with some limited intelligence, and cursed to be resistant to most magic besides fire. One of the darkest weapons of dark wizards everywhere. It seemed they'd found the defence system.

"I don't suppose broomsticks would fare any better?" Hermione asked.

"You-Know-Who probably has someway to deal with them," he agreed. "Maybe not cancelling the flight charms, but making them throw the rider off, or enchanted seaweed to reach up and grab them, maybe."

"Do we have to fight the inferi?" asked Harry.

"You said this was supposed to solvable?" Bill clarified.

"Yeah. That's how You-Know-Who would do it. There must be a way."

"Then it's not fighting them. Even he wouldn't fight that many of them. Anyway, the horcrux will be in the middle. It's standard evil tomb practice. The prize will be on the island in the centre of the creepy lake. The trick is to find how we're meant to get across it." He waved his wand a few more times, and this time, no inferi appeared. "Come on. This way. Be careful."

Bill led Harry and Hermione around the narrow rim of the lake, moving slowly. It took a long time, and Hermione was starting to worry about the length of the mission again. It was hard to judge, but she thought they'd made it a quarter of the way around the lake before Bill held up his hand for a stop. Now, he crept forward even more slowly, waving his off hand up and down as if groping for something. Neither of the students dared interrupt him. Suddenly, his fist gripped around something they couldn't see, and he grinned.

"Gotcha," he whispered.

With a tap of his wand, a coppery green chain faded into visibility, extending from an eye hook on the cave wall above their heads, down into the water. Another tap, and it began coiling itself on the ground at his feet with an ominous clinking sound. A few fathoms later, and a small boat—clearly built for one person—emerged from the water with no disturbance from the inferi.

"Wow," Harry said. "How did you find that?"

"Second rule of cursebreaking: 'What magic can hide, magic can reveal.' Although if you do it right, it's damn near impossible to do it. When we get out of here, I can show you some of the detection spells." He bent down to examine the boat.

"If that's the second rule of cursebreaking, what's the first?" Hermione asked.

"What magic can bind, magic can loose," he said absently. "That's not counting the unwritten rule: don't mess with powerful magic unless you're prepared to face the consequences."

Isn't messing with powerful magic your job? Hermione thought, but what she said was, "Not every equation has a solution."

"True, but it's a little different with physical structures. We can pretty much take as an axiom that it does, and it usually works—Okay, we have a problem."

"What?" Harry and Hermione said worriedly.

"This boat. The enchantments are a little like an age line—oddly. They'll only let one adult witch or wizard cross. Harry, you can come, but Hermione…I'm sorry, but you'll have to stay here."

Hermione swallowed as her anxiety increased. Bill and Harry were more than competent, but that was one less person to help if something went wrong. She nodded her agreement. "But why would You-Know-Who allow underage wizards at all?" she asked.

To her surprise, it was Harry who answered with a nauseous look on his face: "In case he needed to use a kid as a shield to get through the protections."

"Oh…"

"Let's keep it together," Bill said. "We need to get going."

"Harry!" Hermione said before he could get on the boat. She pulled another horcrux-containment box from her handbag and handed it to him. "You remember the spell to seal it?" she asked.

"Lokutharmeth. Yeah. Don't worry. We'll be careful," he said, and he stepped on the boat, wobbling a little as he did.

Bill followed him. He cast a spell that unhooked the chain from the wall, and he levitated the entire coil into the boat itself. It must have been enchanted because it sat no lower in the water now that when it was empty, even though it looked overloaded. It began to move without any further prompting, gliding through the water as silently as the grave, its wake spreading out in ripples that vanished unnaturally quickly, leaving the lake's black surface as smooth as glass behind them. Hermione watched as they drifted further and further away and carefully sat down on the ledge, her knees drawn up to her chin, anxiously waiting and wishing she could do something to help.

Harry had to crouch with his knees on the rim of the boat to fit in there with Bill, constantly wary of falling over the edge. Up close, the lake's perfect appearance was marred. Where it had once looked like a black mirror, now, under the golden light of his wand, he could see a little bit under the surface, and as soon as he did, he wished he hadn't. There were bodies in the water. Easily a dozen just where the boat passed. Pale hands reached up towards the surface, motionless, and yet seemingly constantly grasping. Pale faces, bloated and waterlogged, gazed up at him, their eyes misted over and sightless. Many were still wearing clothes, and he could see both wizard robes and muggle street clothes on them.

Bill said nothing as they crossed, but he grimaced with anger and disgust each time he saw an inferius drift by. For his part, Harry could think of nothing to say either. The boat moved slowly, and it took long minutes for them to cross the lake. Harry also began to worry about how long this was taking.

Finally, they reached the island with a slight bump. Bill motioned for Harry to get out of the boat, and he did, being careful not to touch the water. The island was a low outcropping of rock, as black as the water, though it was visible being bathed in that sickly green light. The source of it was a crystal basin not unlike a Pensieve, which sat atop a pedestal. Most of the light, they saw when they approached, was coming from an evil-looking liquid within the basin. It so bright that Harry had to squint to look at it, even from the edge of the island, and it looked like the sort of thing that would be labelled "toxic waste" on a cartoon show. The basin and pedestal were also glowing faintly, but he hardly noticed in comparison.

"What is it?" he asked softly.

"Nothing good, I'm sure," Bill said. "Dark magic, and a lot of it—dark enough to hide the signature of the horcrux itself."

"So the horcrux is here?" Harry said.

"It has to be. But the potion is blocking my magic…hmm…" Bill pulled a silver potion-stirring rod from his pocket and tried to dip it into the potion, but it stopped an inch above the surface. He tapped it several times, harder each time. When that didn't work, he tried his fingers.

"Bill, don't—!" Harry yelled, but he stopped when Bills fingers stopped just as the rod did.

"It's okay, Harry," he said. "Some kind of barrier—"

"Hello? Hello? Testing. Testing. Can you hear me?" The voice was soft, but they stopped dead when they heard it coming through clearly in the silent cave.

"Hermione?" they both said in shock.

They looked back the way they came and were surprised to see a bright green light—brighter than the basin itself had looked from the edge of the lake. The light wasn't a point either, but rectangular in shape. A tiny, human-shaped silhouette stood in front of it and waved: Hermione. From her silhouette, the panel of light must have been about four feet high and seven feet wide.

"Oh, good. I wasn't sure this would work." The voice sounded relieved.

"Hermione?" Bill said incredulously. "What did you do? How can we hear you?"

The lake was so large it took several seconds for her reply to reach them. "I used the Mylar sheet from my solar furnace—actually, it's a space blanket, but—I levitated it and fixed it in a perfect ellipsoidal section and cast an Imperturbable Charm on it to make it a perfect sound reflector."

"An ellipsoidal sound reflector?" Bill said. He knew enough arithmancy to understand the implications, but he was still surprised it worked so well. "I guess there's no need to ask if you're you. No one else would've thought of that."

"Wait so it focuses—" Harry said.

"Ha ha. Very funny Bi—sorry, what, Harry?" Hermione replied. The delay was long enough that they were getting crosstalk. They'd have to take their conversation slowly.

"I said, it focuses sound?"

"Right. You should've studied conic sections in Arithmancy by now, Harry. It reflects all sound from one focus of an ellipse to converge at the other focus, and vice versa. I wasn't sure it would work over this distance, but I figured it was good enough to detect aeroplanes in the First World War, so…"

"Oh, right. I get it. Professor Vector never talked much about reflections in conics. So what are you doing?"

"I wanted to find a way to help you—and to make sure you're alright. What's happened? What are you seeing?"

"There's a pedestal," Bill said matter-of-factly. "It's about chest-high, and there's a basin on top of it filled with a dark potion."

"Bill says the horcrux is in the bowl of potion," Harry took over. "But there's some kind of barrier over it so we can't reach into it. And it's glowing bright green like it's radioactive or something."

"How big a basin is it?" Hermione's voice called.

"Probably about three quarts," Harry said, and Bill looked up at him in surprise. "I had to cook a lot growing up," he added.

"Can you identify the potion?"

"No," Bill said. "It might be something he or a Death Eater invented. I'm going to try a few things, but I don't think it'll work." Harry watched as he waved his wand in various patterns over the basin, constantly murmuring spells to himself, but Harry could see no change in the potion, not even a ripple. He wasn't completely convinced it was even a liquid. Entombing the horcrux in a block of some exotic ice would be a good trick. "No, it's no good," Bill concluded with a sigh. "It blocks all the magic I can throw at it. Can't charm it or transfigure it. Can't syphon it out. Can't part it or vanish it or penetrate it by hand."

"Then how do we get to the horcrux?" Harry asked.

Bill sighed more heavily. "It's pretty clear what's intended: it has to be drunk."

"No!" Harry said, and Hermione's denial followed a few seconds later.

"Bill, we don't even know what that is," Harry protested.

"What if it's poisoned?" Hermione echoed. "You-Know-Who could use a minion to drink it or something."

"He'd carry an antidote," Harry corrected. "He wouldn't rely on having a minion with him. But she's right; it could kill you."

"I don't think we have a choice," Bill said. "If we want to get the horcrux, it's the only way."

"Bill, no!" Harry repeated, but Bill conjured a goblet before he could stop him and started to lower it to the surface.

"Wait, Bill!" Hermione's voice cut in. He stopped. "There must be other things you can try. Can you pierce a hole through the bottom of the basin?"

Harry tried it and yelped in pain. "Gah! No!"

"What happened?"

"Spell bounced right off. Nearly put a hole through my hand. Can we boil it, maybe?"

"And breath in the fumes?" he said. "That'd make it even worse."

"What about scooping it out?" Hermione suggested.

Bill looked down at the goblet again, shrugged, and dipped it to the surface. It pierced the invisible barrier as nothing else did and came away filled with the glowing potion. Bill's hand also dipped into the the liquid, but it came away completely clean. Then, Bill tried to pour the goblet out on the ground, but the liquid sloshed, but didn't spill out, even when he turned it completely upside-down. "It's no good, Hermione," he reported. "I can scoop it, but I can't pour it."

"What if we use more goblets?" Harry suggested. He conjured a goblet of his own and tried to dip it, but it met the barrier again. "Damn it!"

"The second goblet hit the barrier," Bill said for Hermione's benefit. "It has to be drunk first."

He waited for her reply in case she had another idea, and she did: "Can you make something else drink it? Like a conjured animal?"

Bill tried it, conjuring a rat. It skittered across the barrier without reaching the potion. He offered the goblet to it, but the moment it touched the liquid, it disintegrated in a puff of magic. Harry jumped.

Her voice cut out abruptly. They looked up, and to their horror, the green rectangle on the cavern wall was gone, only a glint of light remaining.

"Hermione!" Harry shouted at the top of his lungs, hoping it would carry. "Hermione are you there? What's wrong?"

SCREECH!

Several inferi leapt out of the water, disturbed by the noise, and Bill clapped his hand over Harry's mouth. Luckily, the inferi dropped back into the water when silence fell. By the time the splashes cleared, the green rectangle was back. A couple seconds later, Hermione's voice came to them. "Sorry! Sorry!" she said frantically. "The charms wore off. I had to put them up again. I'm fine. Do you have any more ideas on the basin."

"If he's smart, on the inside of the basin. There's tricks Cursebreakers can use for that, but they take days or weeks—sometimes longer. I'm sorry, Harry, Hermione, but if we want to get the horcrux now, we have to play by his rules…One of us has to drink the potion."

"I'll do it," Harry said at once.

"No, Harry. You're more valuable."

"I'm not—"

"Yes, you are. You're the Chosen One. Like it or not, your life's worth more than mine. I have to be the one to drink it."

"Think about it, Harry," Bill said. "You said this puzzle was solvable—that You-Know-Who would want a way to get at his own horcruxes. Right?"

"Right…?"

"That means if this is poison, it's slow acting enough to get the horcrux out—and curable. You said yourself he wouldn't take the risk. And that's important because You-Know-Who didn't have any spells to notify him if the shack was breached. He isn't able to keep constant watch here. That means if someone came in here and got the horcrux, they could probably get out again before he noticed. Then, what would You-Know-Who want?"

"He'd want to track them down and kill them," Harry said without thinking.

Bill shook his head: "No, he'd want to track them down and question them—"

"Okay, so he'd want to find them…" Harry said, and then it click. "And be able to find them."

"Exactly. Even if the potion is lethal, it acts slowly enough that someone would present with distinctive symptoms at St. Mungo's first, and he could find them and question them as to how they got through his protections. Only we already know that, and we don't have to go to St. Mungo's."

"We don't?" Harry said.

"No. We can go to Snape. He might even know what this swill is to start with. Plus, Cursebreakers know to anticipate poison." He pulled out a small kit from his robes and retrieved a phial and a small, stone-like object. "Harry, this is a strong purgative potion," he said. "Once you have the horcrux, pour this down my throat. It won't be pleasant. It'll look like hell, honestly, but it'll get as much of the potion out of my system as possible as fast as possible. Then, after I'm done vomiting, make me swallow the bezoar. There's not much that combination won't save you from if you're fast enough."

There was silence for a few seconds. Then, Hermione's voice wafted in: "Harry, I don't like this. In fact, I hate it. But I can't thing of anything better."

"If we split it—" Harry started.

"No," repeated Bill. "You said it yourself. We don't know what this will do. It won't kill us—not fast, anyway, but one of us still has to be lucid enough when it's done to get us out of here."

"What if you're incapacitated before you're done?" Hermione said worriedly.

"Then Harry will just have to make sure I keep drinking." Bill steeled himself and raised the goblet to his lips.

"Bill, no! Bill, no, please—!" Harry cried, but he wasn't fast enough to stop him. Bill chugged the goblet as fast as a frat boy and dipped it into the potion for another glassful. He choked briefly halfway through, but he kept going.

"Harry? Bill? What's happening?" Hermione called.

"Bill started drinking," Harry said, his voice thick and leaden. "He's on the third goblet."

"My God. How is he?"

"Bill?" he asked.

Bill grimaced, his eyes squeezed shut, as he drained the third glass and started on a fourth.

When Bill finished the fourth glass, he gasped loudly and flopped forward over the pedestal, supporting himself on his elbows. He was breathing hard, and his long hair brushed against the barrier over the potion.

"Bill! Bill, are you okay? Can you hear me?"

Bill said nothing. Instead, he reached down with shaking hands and scooped up another gobletful of potion to drink. He choked halfway through this one and nearly collapsed. The goblet would have spilt if it weren't for the magic on the potion. He barely managed to bring it to his lips again and finish it. Harry saw the level of the potion in the basin had dropped quite a bit, but he was growing very worried for Bill, and he hoped his initial estimate of the amount of potion was high. Drinking three quarts of anything would make the average person throw up if they weren't used to it, much less this horrid brew.

"Bill, can you hear me?" he repeated.

The goblet hung limply from the man's hand. He was crying. "I don't want any more…" he whimpered. He didn't sound in pain. He sounded frightened. "I don't want any more…"

"I don't want any more…I don't want anymore…"

Hermione stood perfectly still, her head at the focus of her elliptical reflector, trying to keep her knees from giving out. The words were so soft she could barely make them out, but she wasn't sure she'd ever heard Bill sounding so scared before, at least in person. What on Earth was that potion doing to him?

"Harry?" she called, raising her voice a little to be heard. "Harry, please talk to me."

A few seconds later, the reply came: "He stopped after five." Harry sounded pained and scared himself. "The basin looks about half empty. He won't drink any more."

"Harry…" she said, and her voice caught, "Damn You-Know-Who. Harry, I'm sorry, but I think you're going to have to make him."

"I don't think I can, Hermione," he called back.

"You have to, Harry," she insisted. "He told you to make him keep drinking, and now that he had to be an noble arse and started, he's got to finish the job. If he doesn't, then all of this will have been for nothing. It's too late to try something else."

"I—Bill—okay…okay…I'll do it," Harry said.

Hermione didn't hear exactly what happened after that, but she could hear Bill protesting a moment later: "Don't make me…I want to stop…Stop…"

There was silence, and Bill moaned long and low: "Nooo…Let me go…Let me go…I don't want to…I keep seeing them, over and over…Make it stop! Make it stop!"

"Bill!" Harry said. "It's alright. I'm here. This will make it stop."

There was a silence again in which Hermione guess Bill was drinking his seventh goblet of potion. Her heart clenched when she heard Harry lie to him. Then, she nearly fell in the water when Bill screamed—first wordless and ragged, then desperate and pleading: "AAAHHGGH! No! No, no, no! I can't do it anymore. Don't make me! Dad! Why did he hurt Dad? Why?"

He started babbling incoherently in terror. Hermione thought he sounded younger somehow. She stared at that mote of green light feeling utterly helpless, separated by at least a quart mile of blackness and deadly dark creatures. There was nothing she could do from here but offer encouragement that already rang hollow.

"Don't! Don't take anyone else from me! Please, don't!"

"He's gone mad!" Harry's voice cut through.

"Just keep going, Harry," she said shakily. She hated herself for saying it, but she didn't know what else to do. "You have to keep going."

"Bill, you're alright," he said. "Nothing's happening. No one's being taken from you."

"They're dead! Why did they have to die, Mummy? Why did they die, Mummy?"

Hermione was confused for a moment. Bill sounded delirious. What was he even seeing? A memory? A hallucination? How old was Bill when his uncles were killed? Old that that, she thought.

"Why won't it stop, Mummy? Make it stop! Please, no more! I'll do anything!"

There was a clatter as Bill presumably knocked the goblet out of Harry's hand. Then, there was some grunting and moan, but it sounded like Harry regained control: "C'mon, Bill, it's almost done…" She could hear in Harry's voice how much he hated himself for doing this, but from the silence that followed, she guess he was still pushing Bill to drink—

"KILL ME!"

Hermione jumped again. Bill's shout was so loud it must have torn his throat ragged.

"I can't do it anymore! Just let me die! I just want it to stop…Please just kill me…" His voice trailed off, and he dissolved into incoherent sobbing.

For a long time, Bill's sobbing was all Hermione could hear. Too long—minutes, at least, though they felt like hours. She couldn't hear Harry moving the whole time. Had something worse happened? Had Bill attacked him?

"H-Ha-Harry?" she called worriedly.

There was another long pause before he answered: "I can't do it," Harry called. She could tell from his voice he was nearly sobbing himself. "I can't—I'm sorry, Mione. I just can't do it."

Hermione blushed. It was the first time anyone in the wizarding world had ever called her that name, including George. It was a childish nickname that had annoyed her on occasion in primary school, and the fact that Harry was using it now showed how scared he truly was—a kind of fear different from facing Death Eaters or even dementors—the kind that can only come from seeing someone you care about in what must be terrible anguish.

"Harry, please, you have to keep him drinking," she said. "You've got to be close to the end."

"No…" the weak reply came back. "I can't. I can't do this to him anymore."

"Harry—"

"There's not much left. I'll finish it myself."

"Harry, no!" she screamed at the darkness. "Harry, don't do it! DON'T—!" But she knew it was too late.

Harry didn't handle the potion gracefully, like Bill had at the start. He was strong-willed and stubborn as hell, but she could tell he was unprepared for whatever the potion was. She could hear him gagging, gasping, sputtering, moaning even as he downed the first glass.

"Harry, please!" she called in vain, tears streaming down her face. "I know you don't want to hurt Bill, but you can't! If it does the same thing to you, I can't help you from here. You have to stay lucid. I can't…"

"Augh! God, that's awful," Harry gasped. Then, a moment later, "This is it! I can see it—the locket!" But before Hermione could react he started gagging and moaning again. A minute later, there was a loud clatter—as loud as any sound got through the reflector—of a goblet hitting the hard, stone ground. A moment later, she heard the faint slump of a body.

"Harry!"

There was no answer.

"Harry! Bill! Someone say something."

"I got it." The words were so weak she could barely hear them. "I got the locket."

"Oh, thank God. Harry, use the potion Bill gave you."

Again, there was no answer.

"Harry, the purgative! The one Bill gave you! You have to use the purgative!"

There was silence from a minute. Then, she jumped at the sound of loud retching and moaning. They started violently and just kept going and going. The sounds went on a horribly long time, and no one answered when she called. Which ever one of them it was—maybe both—sounded like he was throwing up everything he'd ever eaten.

Then, even as the retching was still going on, she heard a far worse sound: a loud screech of hundreds of undead voices, punctuated by hundreds of pale hands grasping up out of the water.

"Harry, the purgative! The one Bill gave you! You have to use the purgative!"

Harry moaned and blinked through the pain and the haze of sorrow. He felt like he was dying of thirst, even after downing three gobletfuls of the worst potion he'd ever tasted—and he'd had Skele-Gro before, so that was saying something. He felt like his guts were on fire from his throat down into his bowels. But the worst were the visions. He saw his parents dying—heard his mother screaming. He saw You-Know-Who's laughing face. He saw the basilisk falling on him in the Chamber of Secrets. He saw Lee Jordan and Cho Chang dying in front of him—all dancing before his eyes in nauseating psychedelic distortion.

Bill was lying face-down on the stone floor, still crying and whimpering. In his few coherent words, he was begging for water, but he was too weak to move. Harry knew he must have it about three times as bad as he did. Somehow, in that haze, he remembered the purgative potion and crawled over to Bill and rolled him onto his back.

"Water…" Bill called weakly. "Water…"

"Here, drink this," Harry said as he tipped the phial into his mouth. "This will make it better." And for once, he was telling the truth—he hoped.

He turned Bill back on his side just in time, as he started violently retching. He gagged and retched loudly, over and over again, but nothing came out of his mouth. Harry started to worry that the purgative was a mistake. What if the potion was enchanted to stay in his stomach like it had in the glass?

By now, Bill was soaked with sweat like he'd just run a marathon, and his sweat was glowing faintly green. The potion was getting out of his system any way it could. He tried to push himself onto his hands and knees, but failed. His face was streaked with green as tears were pouring out of his eyes, harder than Harry had ever seen anyone cry before, except perhaps Dobby. Glowing snot dripped out of his nose in large, disgusting dollops, and he was drooling fit to make Dudley look well-mannered. A moment later, a foul odour made it clear the purgative was working just fine at the other end of his system.

Only then did he start vomiting.

Harry retched himself as he saw glowing green vomit pour out in pints over the stone floor. Like the dry heaving before, Bill's vomiting went on and on, soaking what little of him wasn't soaked already in filth. Most unfortunately, Bill rolled over while this was happening and vomited into the water.

SCREEEEEEEECH!

Hundreds of pale, rotten hands thrust themselves out of the water.

"HARRY! BILL!" Hermione screamed. She could see the moving shapes of shambling inferi silhouetted against the green glow, crawling up out of the lake and onto the small island. She saw flashes of spellfire, and she was relieved to see it was from two wands. Then, came the actual fire. She knew from her Defence lessons that no spell yet discovered could make dead flesh impervious to burning. She'd wondered at the time if that was arithmantically provable—if it was a unique solution to the inverse problem of creating an inferius.

But there were too many of them—far too many. Harry and Bill would be completely overrun, especially in the condition they must be in. Hermione couldn't remember the last time she felt so helpless.

"Oh, screw it," she spat.

She summoned a broomstick from her expanded handbag and used a sticking charm to stick the buttons of her basilisk-skin coat to the shaft, and then, crucially, she launched herself high into the air on a ballistic trajectory towards the island.

The defence against broomstick flying turned out to be twofold: a curse to make the broom buck it's rider off, plus deadly stalactites falling from the high ceiling. Hermione clutched her wand in a death grip as she hung underneath her near-uncontrollable broom and waved it lightning-fast in a large pentagram.

"Cittadellissimo!"

It wasn't the debut she'd planned for her Five-Layered Shield—a spell designed for impressiveness as much as practicality—but it was perfect for this situation. On her ballistic trajectory, chosen to avoid other possible traps, she flew near the ceiling, where the stalactites didn't have as far to fall, and they whittled away the layers of her shield one by one slow enough for her to keep up with reforming them.

A minute later, she was falling towards the island at top speed and screaming her head off. She had just enough time to aim the still-bucking broom where she wanted to land and cast a powerful Banishing Charm. A dozen inferi toppled away like bowling pins, and the force of pushing against the ground slowed her fall until she dropped and rolled onto the ground.

"Hermione?!" Harry and Bill said in shock. And then, a moment later, they both shouted, "Incendio!"

Hermione spun around once and took in the scene. Harry and Bill were covered in scrapes and minor burns, but otherwise looking remarkably well for the circumstances, which meant they still didn't look very good. They were barely holding the inferi at bay. Her timely arrival had probably saved them from being overrun from behind. Yet they were both pouring out more fire than she thought she would be capable of, and she hadn't been poisoned. She rarely got a chance to see Harry fight all-out, but when he did, he was a powerhouse.

She ran to their side, and they stood back to back to back in a triangle, the box that she hoped contained the horcrux lying between their feet. Deciding quickly, she switched to her red oak wand in her left hand to cast an Incendio, while with her right, she drew Snickersnack from its scabbard.

Her fire spells were indeed weaker than Harry's or Bill's—not exponentially so—probably not even by half, but they were weaker, just as she'd be slower than a trained sprinter or weaker than a wrestler in a higher weight class, and it make her a weak point. But Hermione was better-equipped. Snickersnack cleaved through the rotting flesh and bone of any inferi that got through her fire line like butter. It was unnerving, doing that. She'd never had cause to use her sword on a person before, and while the inferi weren't alive, they looked similar enough to make her feel like she was cutting real people down with it. It wasn't a good feeling.

She started by just cutting the inferi's heads off, since she'd seen one or two zombie movies in her time. (And thank Merlin inferi weren't contagious like horror film zombies.) But when she did that to the inferi, they just kept coming at her, headless, so she went for the arms and legs, or even across the lower torso.

Hermione had the advantage here in some ways, she thought as she sliced an arm and a leg of an inferius and toppling it over, whilst still struggling to maintain her fire line. The best and worst quality of inferi was that they were nothing but dumb beasts—the worst because they just kept coming no matter what, but best because they didn't have the brains to avoid the most obvious of attacks. It still wasn't easy. She tried to think of anything else she could do against them. Not many of her other curses applied, even her darkest curses.

"Non Perturbare!" she cast.

That helped. An Imperturbable Charm on the ground turned the ground frictionless, and that slowed down the inferi that were climbing out of the water, but the ones already on the island simply crawled over each other and kept coming. And she wouldn't be able to maintain it over such a large surface area for long.

What else? Extract magnesium from the rocks? No, she'd probably just blow herself up doing that. Not enough carbon to make enough oil to get them all. Splitting water into hydrogen and oxygen? Same problem. She couldn't think of any other way to fight them with magic. They were impervious to most normal spells.

Harry stopped casting and then, to Hermione's surprise and Bill's horror, picked up a handful of ash from the burnt bodies at his feet. Hermione and Bill cast even harder to stop the renewed intensity of the assault. Harry was waving his wand over the ashes.

"Harry, what are you—AUGH! —doing?" Hermione asked as she burnt one inferi and sliced another.

"Those nanowire things you used in the Department of Mysteries," he said. "You showed me how to make them. I figured we could tangle them up or something."

Hermione soon realised he had rearranged the atoms in the ashes to make a spool of very fine nanotube wire like her tripwires, and he began levitating it and unspooling it over a group of a dozen or so inferi. "I don't know if that'll work without a source of tension—" she started.

Harry quickly pulled the floating tangle of wire down on the inferi, and they became caught in it instantly, the loops cutting deep into their rotting flesh and in some places sawing off whole body parts every time they moved. As they struggled against each other, it cut even deeper, but it seemed to catch against their bones. They were maimed by deep gashes, but not dismembered, and they kept shambling towards the trio.

"Stop them!" Hermione warned. "They'll slice us up with those wires as easy as they do themselves!"

All three of them turned their strongest fire spells on that group, and they were burnt to ashes before they could reach them.

"Sorry," Harry said.

"It made sense," she admitted. "Incendio! It's like Shadow Square wire in Ringworld. It's just not strong enough—Incedio!"

She tried to think. Could she improve it? She'd calculated before that a wire about a quarter of a millimetre in diameter was strong enough to cut an unprotected human clean in two with enough force behind it. It was just that the shambling inferi weren't putting enough force behind it as they moved. If only they had something sharper, like that razor wire the military used these days.

Wait, that was it!

"Cover me!"

She dropped her sword, dropped down on her hands an knees and grabbed two handfuls of ash.

A millimetre wide, a tenth of a millimetre thick, a diamond-shaped cross-section not too different from her sword, giving the same cross section and strength as the wire, but massively greater cutting power. It would work. At that thickness, two hundred metres of the stuff would only weigh a few ounces.

She couldn't touch it. It would cut her fingers clean off with the lightest tug, like the poor child in Niven's book. When she got home, she was making some nanotube mesh gloves so she could actually handle the stuff, but for now, she levitated it, like Harry had, using both wands for precision work as she shaped it. She didn't bother with a spool—just a coil, but she was careful about how she designed it. It wasn't spring-loaded like razor wire was, but it could unfold like an accordion. She was ready.

She stood up, her face a mask of determination that spelt doom for any enemy who crossed her, if the inferi had any brains to read it. "Stay close to me," she ordered with such conviction that Harry and Bill press against her sides without thinking, still spraying fire as fast as they could. "When I give the signal, drop the fire and duck, okay?" she said.

"Um, sure," Harry said.

"Okay, but this better be good," Bill agreed.

"NOW!"

As soon as Harry's and Bill's heads dropped below her arm level, Hermione spun in a circle, swinging her arms around, and the razor thread uncoiled and dropped onto the inferi. She couldn't see it, in the darkness, but she knew where it was: two hundred turns of razor thread a foot wide, spaced a few inches apart in a circle twenty feet in diameter. The now-unhindered inferi shambled into it, getting tangled worse than Harry's attempt had done. The corpses strained against the wires again, but this time, just when she thought the sight couldn't get any more horrifying, it only took a few seconds before dozens of Inferi simply fell to pieces, leaving nothing but writhing piles of rotting flesh.

The coils of razor thread were still lying there on the ground, tangled with the writing flesh. With weak banishing charms, they pushed the coils back into the next wave of inferi. The new inferi got their feet caught in it and tripped, tearing themselves apart from the bottom up.

And that was enough that Hermione lost her supper. None of the other horrors she'd witnessed this night had been enough to do it, but that sight did it. Moments later, Bill started dry heaving. Even the hardened Cursebreaker couldn't stand it. Harry followed not long after. When Hermione collected herself, she was horrified to see Harry had vomited up a large amount of glowing green sludge. When she looked at Bill, he was still dry heaving and sweating profusely. He looked dehydrated.

"Oh, Harry, you stupid, selfless—" she muttered before they needed another round of Banishing Charms for the inferi.

The dead bodies fell again and again to the razor thread. There were so many. They banished the dismembered parts into the water so they wouldn't be buried under them. They just kept tearing them apart in wave after wave. It was just as horrible to watch every time. Razor thread would never be this effective against wizards, Hermione was sure—or muggles either except in the direst of circumstances, or indeed, even against dumb animals that had a modicum of self preservation. But the inferi were cursed not only to act like dumb animals, but to keep attacking with a ravenous bloodlust no matter what happened. So the just kept coming and coming until finally…they stopped, and the lake turned disturbingly calm again.

"They're…they're gone," Harry whispered.

"K-killed them all…" Bill rasped. Hermione looked at him and saw he was on his hands and knees staring out at the lake in horror, shaking badly. "H-hundreds of them…killed them…"

Even Hermione hadn't been able to get an accurate count, but she thought there had been about three hundred inferi. Three hundred people that You-Know-Who had killed and turned into his sick puppets. It nearly made her vomit all over again to think about it, so she forced the thought down.

"Harry, you got the horcrux?" she asked.

"It's in the box," he said. He picked up the carrying case and rattled it as a demonstration.

"We should go, then. Bill?"

Bill turned and looked up at her, and Hermione was taken aback when she saw the look in his eyes: he was scared of her. That was not something she was prepared for.

"Harry?" she said helplessly.

Harry helped Bill to his feet and supported him on his shoulders over to the boat. Hermione took the horcrux. The man looked dead on his feet, and Harry didn't look much better. Fortunately, the boat was still intact, but it could still only take two of them. Bill practically fell into the boat and lay on his back. Harry gripped the prow and leaned over.

"Harry, are you going to be okay?" she asked.

"D-don't know…" he muttered. The adrenaline was wearing off.

"Harry, that potion…it made you see your worst memories, didn't it?"

He looked up in surprise: "How did you know?"

"I wasn't sure, but I heard Bill screaming." Unfortunately, she didn't think a Patronus Charm would help with that. "How much did you drink?"

Harry shrugged: "'Bout a third as much as he did. Still felt like I was dying."

"Okay, you'll have to take the boat. Take the horcrux, too, just in case. Bill, is it safe to go in the water?"

Bill didn't answer.

"Bill!"

Bill was shaking at the bottom of the boat. He looked delirious and unresponsive. He was still sweating, though she didn't know where the sweat could be coming from after what the purgative seemed to have done. His eyes were sunken, and the glowing remnants of the potion made him look like a corpse.

"We've got to get him out of here!" Hermione said. "And the boat's too slow. I'll have to risk it. Harry, find that rope he had."

Harry flopped into the boat and searched his robes, pulling it out. Hermione tied it tight around her waist and tied the other end to the prow of the boat, and she held her broomstick with her other hand, just in case. "Banishing Charms again," she said. "Push it along. The boat's too slow on its own. And get him some water."

"Aguamenti!" Harry said. "Damn it, Aguamenti!" Harry had apparently conjured another goblet and was trying to fill it with water.

"What's wrong?" Hermione asked.

"The water's vanishing when I try to fill it. Look!" He demonstrated again, and Hermione saw the water vanish the moment Harry poured it into the goblet as fast as if he were pouring it into a sieve.

"It must be the cave," she said. "It's still trying to screw us."

"But the lake's not vanishing," he said. He started to dip the goblet into the water.

"Are you crazy? That's had dead bodies in it—cursed ones!" she gasped. "That could kill him the same as the potion. I probably shouldn't even—Of course, Ebublio!" She cast a Bubble-Head Charm so that she wouldn't get any water in her nose or mouth. She was relieved that it worked. "We have to get him back to Fleur and Sirius." She jumped into the water. It was even colder than outside. "Push us off."

The boat lurched and started to move. The now-empty lake offered no resistance to Hermione, half-floating on her back and doing her part to push them along. With Banishing Charms, it took less than five minutes to get them to shore, but casting Banishing Charms continuously for five minutes was still no picnic, especially after all the fighting they'd done. Hermione was exhausted by the end of it, and Harry looked ready to pass out. When they reached the shore, Hermione grabbed her Mylar blanket and directed Harry to push them along the shore in the boat. It would have taken too long to dragged Bill along the edge on foot. She ran alongside on the narrow catwalk, pulling the boat with Summoning Charms. Again, there was no disturbance from the lake.

Finally, they reached the entrance. Hermione pricked her finger to open the archway, and she and Harry carried Bill up and out of the water and down to the tunnel. The tide was still out, thank Merlin, although with Bubble-Head Charms, she realised it had never been quite as urgent as she'd thought. She cast a Bubble-Head Charm on Bill anyway, since he couldn't keep himself afloat.

On the outside of the tunnel, they came out into the crashing waves once again, and Hermione did her final trick. Her abused broomstick was waterlogged and on its last legs, but she managed to load all three of them onto it and lift them up to the rock outcropping where they'd first arrived.

"Good. I'll take Bill. Back to Sirius's place on three. One…two…three!"

The trio reappeared, filthy, soaking wet, and half frozen in Sirius's living room and collapsed to the floor.

"Harry!"

"Bill!"

"Hermione!"

Sirius, Fleur, George, and Fred rushed forward to help them up. George hugged Hermione, heedless of the grime she was covered in, then checked her over to she if she was alright. Of course, she was in the best shape of the three—mostly just exhausted. "Help Bill," she said.

"Mon Dieu!" Fleur gasped, holding Bill. "What 'appened to him?" She looked up at Hermione with fire flashing in her eyes: "What did you do?"

"He drank two litres of a dark potion and then a purgative and then fought an army of inferi, the idiot," Hermione said. The others gasped in horror, but she didn't have time for them. "Someone bring water. Hurry," she said. She looked at Bill again. "And salt. He'll need salt."